Method and apparatus for evaporating liquids



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N. TESTRUP l METHOD 4Arm APPARATUS Fori BvA'PpRATING LIQI'JIns Filed `lm g. 9/1'920 l 8 Sheets-Sheet atented July 15; 1924..

PATNT OFFICE.

NILS TESTRUP, F LONDON, ENGLAND, `ASSIGNOR T0 TECHNO-OHMICAL LABORA- TORIES LIMITED, OF CLAPHAM APARK, LONDO'N, ENGLAND.

METHOD AND APPARATUS FOR EVAPO'RATING IIQUIDS.

Application led August 9, 1920. Serial No. 402,320.

To all whom t may concern:

Be it known that I, NILs TEs'rRUP, a subject of the King of Great Britain and Ireland, and residing at 47 Victoria Street,

London, S. W. 1, England, have invented certain new and useful Methods and Apparatus for Evaporating Liquids, of which the following is a specification.

This invention relates to improvements in connection with evaporation, distillation and similar operations, `and especially those of the lm type of Patent No. 1,150,713 of 1915 and has for its object to provide improved methods and means for effecting these operations.

In all evaporative apparatus at present in use diiiiculties `of a more or less serious kind arise, due to scale being deposited upon the surfaces from which the evaporation 2o takes place. These surfaces tend .more or less rapidly to lose their evaporative eliiciency as such deposits take place. This has led to the use of a wide variety of surface cleaning methods and devices. The evapo-`I rative surfaces of such evaporators are usually those of tubes forming the structure,I

and it is necessary to clean them at -intervals when the -tubes are out of service.

In application SerialNumbe 358,088 filed February 12, 1920, co-pending herewith it has been proposed to employ rotating drums or like surfaces as dryers of liquids containing solids in suspension or solution, and thus to obtain more or less dry solids, the reverse surfaces of the drum being heated by evapo-i rated fluid after raising its vapour temperature and pressure to the required extent.r It has now been found, however, that this type of device can be applied advantageously to e0 the'evaporation or distillation of liquids, the

liquid ilm being maintained practically continuous over the evaporating surface.

Now the present invention consists in fluid evaporating or distilling rneans comprising 15 sheet metal surfaces for the evaporation, carrying upon one side a liquid lm and heated upon the otherside by the vapour of evaporated liquid after its temperature and pressure have been suitably raised, together with scale removing means in con-4 tact with and movable relative to the evaporating surfaces.

The inventionalso consists in a suitably enclosed rotating hollow drum evaporator u pon the outer surface of which drum the l1qu1d` to be evaporated is spread as a thin film, and to whichA surface is applied at a suitable point a scraping or brushing deviceV adapted to continuously remove any scale deposited during the evaporation eEected by the vapour of evaporated liquid after its temperature and pressure have been suitably raised.

The invention further consists in combinations of such drum evaporators in stages suitably chosen in relation to the rise of boiling point of the liquid or the economy of the evaporating surfaces or both.

The invention also consists in suitably corelating and separating the ingoing and outgoing fluids.

The accompanying more or less diagrammatie drawings show by way of example several various embodiments of the invention. v

In these drawings Figures 1 and 2 show a plain cylindrical drum dipping into the liquid.

Figures 3 and 4 show a similar drum, but arranged with a fee roller to apply the liquid to its surface. p

Figures 5 and 6 show a corrugated drum which is wetted by dipping into the liquid.

Figures 7 and 8 show a corrugated drum with buckets for distributing the liquid over the surface thereof. I

Figures 9 and 10 show a corrugated drum with feed)roller' distributing means, and

Figures 11 and 12 vshow a corrugated drum with means for spraying the liquid over the surface thereof.

Figures 13, 14, 15 and 16 show the application of deposit removable means to the interior surfaces of the evaporating vessel.

i n carrying this invention into-effect in one of the forms given by way of example, I take a drying drum a of the known type and having a hollow spindle a and enclose it in a casing b provided with an outlet pipe c for the steam4 connected to a compressor d adapted to raise its temperature and pressure, to say from 30 CL to 5 C. above the boiling point of the liquid. The delivery e of the compressor d is connected through a suitable stuiing box 7" to the inside of the drum. The drum is mounted on suitable .bearings Z1', b2 in the easing and provision is made `,for withdrawing .25 ployed as `hereinafter described.

the condensed water therefrom, say bythe syphon pipe g, which epasses through another stuii'ng box f. u The lower part of the casing b is formed as a reservoir b3 for the ingoing liquid which is admitted by a float controlled valve h after being regeneratively heated by thel outgoin condensate in the heat interchanger i. he drum a at its lower side dips .intothe liquid in the reservoir b so that as it rotates its surface continuously carries. over a thin film of the liquid.

A scale removing device 7' is conveniently placed about the lowest part of the drum, and this device may beY arranged to act in p a partitioned ofi' part of the reservoir. The scale removing device is shown as a simple revolving brush which is suitable` where the scale is soft, as is usually the case where a small difference in temperature is employed between the evaporating and heating surfaces. Or again, a rubber or like strip suitably supported may be used or where necessary a metal scraper ma be emn some cases, especially where a large amount of scale forming material exists in the liquid to be evaporated, provision may be made for continuously removing the scale from the apparatus. l s

The drum is driven at such a s eed as `will provide for the maintenance o a uniform film of li uid thereon and as the liquid *is concentrate in the apparatus it is removed by means of the specific gravity controlled valve in the vessel Z positioned at the side of the casing b. The vessel l coml municates with the bottom and the upper portion of the reservoir b3 b means of pipes Z Z2 and' it contains a oat m connected to the end of the lever m which controlsva valve giving access to the discharge p1 e n.

n the arrangement shown in Figures 3 and 4, the drum a does not actually dip into the liquid and a contacting roller Ik dipping into the liquid is provided t spread the liquid 'upon theJ drum.

A metal scraper o which may be hinged to the top of a perforated' partitionzp is res'iliently pressed against the surfe/ee of the drum and acts to remove the scale or other .deposited matter therefrom. ,In other respects this arrangement is similar to the oneshown in Figures 1 and 2 and similar letters of reference for the various parts are employed therein.

In Figures 5 and 6 the plain cylindrical drum is replaced by a corrugated surface made upfof a series of four hollow disc-like membersg, g', g2 andgs. mounted upon and 1commun'i'cating freely with the interior of V the hollow drum spindle a. p f-i'z-'The drum is enclosed`in a casing b yas hereinbefor'e describedv the lower portion of which forms a reservoir in which the liquid is maintained at a suitable level by vmeans of the oat valve L.

The liquid level in this case is of such a height that itl will effectively wet or apply a film of liquid to` the sides of the disc members. Scrapers 0`2 suitably connected to i the casing in a substantially vertical or other convenient position are provided for cleaning the sides of the discs and in other respects the apparatus resembles those previously described.

In Figures 9 and 10 substantially horiz'ontal rollers p are provided for applying the liquid film to the disc surfaces, the rollers operating in channels or troughs s\con nected to the interior of the casing so as to lie betweenthe disc-like members and fed with the liquid by means of pipes t connected to the discharge of a liquid circulating pump u which draws its supply from the reservoir b3 in which a suitable level is maintained.

In the arrangement shown in Figures 11 and 12, the liquid is applied to the heating surface by spray pipes 'z; receiving their `supply from a circulating pump u and scrapers o2 are provided for cleaning the surface adequately before the application 'of the liquid film thereto.

The drum may be in some cases of a hard and polished material, or it may again have a somewhat rough outer surface. The surface of the drum may have metal gauze, or even absorbentinaterial uponit.

It is found that with'this evaporator complex liquors, such as waste sulphite lyes, can be evaporated efficiently and all the serious difficulties of scaling at present existing are avoided as the evaporating surfaces can be 'kept Vcontinuously free from scale. l

An apparatus which is quoted by way of example only was provided with an ordinary steel plate, bent and welded into a tube.

The fil-m in this case was picked up at the speed of about twenty revolutions per minute, and was a practically perfect film free from splashing or other inconvenience;

Some results obtained were as follows I When -evaporating ordinary water works mately one-sixth less than the maximum, and

when evaporating saturated solution of gypsum with Scrapers oi', the efficiency in .four hours is reduced from about 8 to 5 and after further eight hours to about From the foregoing it appears that the cheapest possible Surface can be used for carrying out the process and that maximum evaporation can be obtainedy continuously whatever be the material evaporated, also,

that the apparatus may be the simplest conv ceivable for the purpose with nothing moving exceptthe revolution of the drums.

In some cases matter may be carried over in the form of vapour or in suspension in the vapour, which will deposit upon the interior surface of the evaporatingvessel and thus diminish its efliciency.

Under such circumstances, Scrapers as shown in Figures 13 and 14 may be applied to the interior surface of a plain cylindrical rotating drum, said Scrapers comprising guides 1 suspended from straps 2 Vriding upon the trunnion tube A1. The said guide rods carrying adjustable brackets 3 having a longitudinal fulcrum bar 4 upon'which the scraper 5 is hinged. The guide bars also carry slidably mounted weights 6 resting upon a longitudinal bar 7, attached bylevers S to the scraper 5 and by means of which the Scrapers are held in contact with the interior Surface of the drum.

Figures 15 and 16 show one section of corrugated drum with inte-rior deposit removal means which take the form of Scrapers 9 arranged in a substantially vertical direction `and supportedupon a stand pipe 10 reaching to near the bottom of the Section and communicating with the condensate outlet p pipe 11, by which the condensed vapour is removed from the apparatus.

Having now described my invention, what I claim as new and desire to secur by Letters Patent is 1. A method of reducing thc temperature dierence required for. transmitting heat through a partltlon for vaporizing liquids by the heat of their own vapour raised in temperature by compression, comprising continuously dislodging by relative movement of deposit removal means and said partition any material deposited on the latter from a thin film of said liquid or'the vapour thereof.

2. A method Vof reducing the temperature difference required for transmitting heat through a partition for vaporizing liquids by the heat of their own vapour raised in-temperature by compression, comprising continuously dislodging from both sides of saidl partition, by deposit removal'means, any material deposited thereon.

3. Apparatus for carrying out a method of reducing the temperature difference required for transmitting heat through a part1t1 on 'forsvaporizing liquids by the heat of their own vapour raised in temperature by compression, comprising in combination a moving heat transmitting partition, means for vapplying a thin ilm of liquid matter thereto, means for withdrawing, compressing and returning to the other side of said partition vapour evolved from said film and means for dislodging any, deposit formed upon the surfaces ofl said partition.

4r.v Apparatus for carrying out a method of reducing the temperature difference required for transmitting heat through a partition for vaporizing liquids by the heat of.

their own vapour raised in temperature by compression, comprising in combination a moving heat transmitting partition, means for applying a thin film of liquid matter thereto, inoving mechanism for withdrawing from one side and returning, at a higher temperature and reduced volume, to the: other side of said partition vapour evolved from said film and means for dislodging deposited matter from both sides of said partition.

5. Apparatus for carrying out a method of reducing the temperaturedierence required for transmitting heat through a partition for vaporizing liquids by the heat of their own vapour raised' in temperature by compression, comprising in combination a rotatable heat transmitting partition, means for applying a thin film of liquid matter thereto, a mechanical compressor for withdrawing vapour evolved from Said film and returning it at a higher temperature as heatingmedium for said partition and lmeans 'for keeping the partition free from deposit.

6. Apparatus for' carrying out a method of reducing the temperature difference required for transmitting heat through a par# tition .for vaporizing liquids by the heat of their own vapour raised in temperature by vin a compressed and hotter condition and means, for removing vdeposit from the outside and inside surfaces of said vessel.

-7. An` apparatus for expelling vapour from liquid material by the re-utilization of latent heat, comprising a rotatable heat transmit-tingpartition, means for applying a film of liquid material onto the surface of said partition, means for collecting the vapour given off by the said film of material, means for raising the temperature of said vapour by compression and returning it as the heating medium to the other ,side of said partition and means for dislodging deposit from both sides of said partition.

8. An apparatus for economizing heat when evaporating liquid matter comprising in combination an enclosing chamber, a rotatable closed vessel in the form of a drm L' in. said chamber, a mechanical compressor,

a conduit connecting said chamber to the inlet of said compressor, a conduit connecting the discharge from said compressor to the interior of said drum, means for spreading a ilm of liquid matter on the exterior of said drum, means for evacuating from said drum liquid of condensation and means for removing any material de osited upon the interior or exterior of sai drum.

In testimony whereof I have signed my name to this specification. v

NILs TESTRUP. 

